This invention relates to metallized fabrics which are durable to washing and wear. They can be used to down-proof articles in which they are used as linings, e.g., down and fiber filled, insulated articles of clothing and sleeping bags.
Metallized fabrics are utilized to reflect radiant heat emitted by the body and thus provide effective heat insulation, particularly for outdoor use and in cold weather climates, e.g., winter apparel and sleeping bags.
U.S. Pat. No. 4,569,874 to Kuznetz discloses lightweight sportswear fabric for cold climates which comprises a composite fabric having vapor-permeable laminate formed by a core layer of hollow fibers acting as a thermal blanket between inner and outer skins. Both faces of the inner skin and the inside face of the outer skin are metallized to render them reflective while the outside face of the outer skin is blackened to absorb solar energy. Radiant heat from the wearer is reflected by the outside face of the inner skin while convection heat from the wearer""s body passes by conduction through the inner skin of the laminate to be absorbed by the core layer. Solar heat absorbed by the blackened face is conducted through the outer skin to be absorbed by the core layer. Infrared energy loss from the core layer is minimized by internal reflection from the reflective inside faces of the skins.
U.S. Pat. No. 5,750,242 to Culler discloses a fabric which provides thermal image masking in mid and far infra-red region without compromising the effectiveness of visual and near IR camouflage or comfort level. The material incorporates a metallized microporous membrane into a typical article of clothing or covering, e.g., tents, which suppresses thermal imaging. An air permeable, moisture vapor transmitting, waterproof material having a metallized membrane is laminated to a textile backing and the metal in the metallized membrane forms a discontinuous layer at the surface and on the pore walls adjacent the surface of the microporous membrane. This provides an air permeable, vapor transmissive, waterproof material which suppresses thermal imaging of objects behind the metallized membrane.
U.S. Pat. No. 5,271,998 to Duckett discloses a lightweight metallized fabric which can be used in an automobile cover. The fabric is made by vacuum metallizing with aluminum and applying a finishing solution comprising a urethane, acrylic, fluorocarbon polymer emulsion, drying the fabric at 320xc2x0 to 400xc2x0 F. and optionally calendering the fabric after drying.
U.S. patent application Ser. No. 09/148,182, filed Sep. 4, 1998, (Case No. 2049) discloses a metallized fabric of improved washfastness which comprises discrete metal particles encapsulated within a cross-linked polyurethane latex. U.S. patent application Ser. No. 09/400,511, filed Sep. 20, 1999, (Case No. 2097) discloses a metallized fabric of improved washfastness which comprises discrete metal particles encapsulated within a cross-linked polyurethane latex, wherein the metal particles are treated with a primer coating composition comprising the reaction product of a copolymer comprising at least two different monomers: (i) a phosphate-containing vinyl monomer and (ii) a second, separate vinylic monomer containing at least one reactive group capable of covalently reacting with the cross-linking agent present within the polyurethane latex coating.
It would be desirable to provide insulated metallized fabric articles suited to use in cold weather applications such as insulated apparel, sleeping bags, etc. which comprise a fabric having a metal-coated side and an uncoated side which fabric is of improved washfastness. Moreover, it would be desirable to provide metallized fabric articles that do not allow the migration of natural and synthetic insulations, such as hollow fibers or down, through the fabric so as to contain the insulation within the article during normal use and washing.
In one aspect, the present invention relates to a durable, lightweight metallized fabric which can be used as a lining for insulated articles and which is resistant to migration of insulating materials through its thickness. The fabric comprises: a metallic side having a metal coating containing discrete metal particles, a non-metallic side, and a cross-linked polyurethane latex coating over both sides which encapsulates said metal particles. The fabric can be calendered to an extent sufficient to reduce migration of insulation through its thickness.
In another aspect, the present invention relates to a method of preparing a metallized fabric which comprises
i) providing a fabric,
ii) coating one side of said fabric with metal particles,
iii) coating both sides of said fabric in a cross-linked polyurethane latex comprising a polyurethane dispersion, a cross-linking agent, an inhibitor, and optionally, a catalyst to initiate cross-linking of said polyurethane dispersion, to encapsulate said metal particles within said polyurethane latex; and
iv) calendering said fabric to an extent sufficient to reduce migration of insulation through its thickness.
In yet another aspect, the present invention relates to an article of clothing containing insulation and having an interior lining of metallized fabric resistant to passage of said insulation through its thickness, which comprises a metallic side coated with metal particles, a non-metallic side, and a cross-linked polyurethane latex coating over both sides to encapsulate said metal particles within said polyurethane latex, wherein the metallic side faces a body surface of a wearer. The resistance of the fabric to passage of the insulation can be increased by calendering the metallized fabric.
Without limiting the scope of the invention, the preferred embodiments and features are hereinafter set forth.
The present invention relates to a metallized fabric of improved washfastness which comprises a metallic side, a non-metallic side and a cross-linked polyurethane latex coating on both sides. The metallic side comprises a metal coating containing discrete metal particles encapsulated within the cross-linked polyurethane latex. The encapsulated metal coating serves to resist corrosion of the metal particles adhered to the fabric surface to substantially eliminate removal of such metal particles from the fabric substrate due to abrasion encountered during fabric use, atmospheric conditions and/or harsh laundering conditions.
Any fabric can be utilized in this invention provided that the polyurethane latex thoroughly coats the metal particulate coating of the fabric so as to substantially prevent contact between the metal and atmospheric oxygen or harsh oxidizing (and thus corrosive) chemicals present within laundry applications. Fabric comprising polyamide yarn, e.g., nylon, is most preferred. However, any natural fabrics such as cotton and ramie, or any synthetic fiber material such as, polyester, other polyamide, polypropylene, polyester-polyurethanes such as Lycra (Tradename), available from E. I. duPont deNemours and Company, Wilmington, Del., and the like; or any blends of synthetic fibers may be utilized within the inventive fabric. While plain weave construction is preferred, fabrics may be woven in plain, rip-stop, twill, satin or crepe constructions. The fabric yarns may range from single to double ply, 30 to 300 denier and 34 to 150 filaments. The preferred yarn in both the warp and filling direction is single ply, 40 denier with 34 filaments. It is preferred to use a flat warp yarn and textured filling yarn, but either type may be used in either the warp or filling. The preferred finished fabric yarn count when using 40 denier yarn is 170 warp yarns per inch and 140 filling yarns per inch. However, the warp yarn count when using 40 denier may vary from 80 to 200 and the filling from 80 to 200. Additionally, the yarn count can vary considerably depending on the yarn denier.
Prior to metallizing, the fabric can be scoured clean and dried. At this point, the fabric can be metallized, preferably with aluminum. This process includes applying a very thin layer of aluminum to a surface of the nylon fabric with a technique known to those of ordinary skill in the art of metallizing fabrics and film.
The preferred method of metallizing the fabric is by vacuum metal vapor deposition. However, metallizing of the fabric may be accomplished by any process which can be used to deposit metal onto a fabric and which bonds the metal to the fabric. The metallizing step may be carried out by other techniques such as metal sputtering, plasma treatments, electron beam treatments, chemical oxidation or reduction reactions, as well as currentless wet-chemical deposition.
The surface of the fabric may be modified by flame treatment, plasma discharge or corona discharge treatments to enhance adhesion of the metallic coating to the fabric before the metallizing step and/or before the encapsulation process to enhance adhesion of the polyurethane to the fabric.
Any metal generally utilized within a coating for fabrics may be utilized within this invention. The most common metal for this purpose, aluminum, is preferred because of its low cost and superior performance characteristics including radiant heat reflection in cold weather fabrics. Other metals which may be utilized include copper, gold, silver, nickel, zinc, titanium, chromium, vanadium and the like.
The metal layer on the fabric substrate in this invention preferably comprises aluminum, deposited by a vacuum deposition technique on the fabric substrate, with a thickness lying in the range of from 200 to 300 angstroms, i.e. 20 to 30 nm. This metallizing process is available from various vendors, including Diversified Fabrics of Kings Mountain, N.C. and National Metalizing of Cranberry, N.J.
The present invention utilizes a polyurethane latex over the metal coating of the target fabric to provide a barrier to corrosive elements resulting in a long-lasting radiant heat reflecting fabric.
The polyurethane component can be a waterborne aliphatic or aromatic polymer which provides a soft hand to the fabric substrate. As such, the preferred polyurethane is a dispersion comprising a polyurethane having an elongation of at least 150% and, conversely, a tensile strength up to 7000 psi. Particular examples of such dispersions include those within the Witcobond (Tradename) polyurethane series, from Witco Corporation, New York, N.Y., such as W-232, W-234, W-160, W-213, W-236, W-252, W-290H, W-293, W-320, and W-506, with W-293 being especially preferred. Acrylic polyurethane dispersions may also be utilized provided they exhibit the same required degree of elongation and tensile strength as for the purely polyurethane dispersions.
Any cross-linking agent compatible with polyurethanes may be utilized within this invention, particularly those which have low amounts of free formaldehyde. Preferred as cross-linking agents are Cytec (Tradename) M3 and Aerotex (Tradename) PFK, both available from BFGoodrich Co., Akron, Ohio. Any catalyst, which is generally necessary to initiate and effectuate cross-linking of a polyurethane dispersion, which is compatible with both a polyurethane and a polyurethane cross-linking agent may be utilized within this invention, e.g., Cytec (Tradename) MX, available from BFGoodrich Co.
Adhesion promoters which serve to promote adhesion between the aluminum and the polyurethane can also be present in the cross-linked polyurethane latex. Such adhesion promoters include polymers selected from the group consisting of silanes and phosphates. An adhesion promoter phosphate polymer can be applied in 0.1-1.0% percent add-on the weight of the fabric (owf). Amino-silane compounds available from Gelest in Tullyton, Pa. can be used in the 0.1-2.0% add-on owf.
The cross-linked polyurethane latex of the invention may be present in any amount and concentration within an aqueous solution for use on and within the target fabric. Table 1 below indicates the difference in performance of the cross-linked polyurethane latex in reference to its concentration and dry solids addition rate on the fabric surface. Preferably, the concentration of the polyurethane is from 5 to 100% by weight of the utilized aqueous solution; more preferably from 10 to about 75% by weight; and most preferably from 25 to about 50% by weight. The coating addition rate measured as the percent of dry solids addition owf of the cross-linked polyurethane dispersion is preferably from 3 to 50% owf; more preferably from about 6 to about 40% owf; and most preferably from about 15 to about 30% owf, say about 10%.
As noted below, the basic procedure followed in applying this cross-linked polyurethane dispersion entails first providing a metal-coated fabric. Next, the latex is formed by combining the polyurethane with the cross-linking agent and, optionally, a catalyst to effectuate such cross-linking of the polyurethane. The resultant latex is then diluted with water to the desired concentration which will provide the most beneficial washfastness of the metal coating after treatment. The metal-coated fabric is then saturated with the resultant aqueous solution of the polyurethane latex with the excess being removed. Such saturation and removal of the latex may be performed in any standard manner, including dipping, padding, immersion, and the like for initial contacting of the dispersion; and wringing, drying, padding, and the like for the removal of the excess. The treated fabric is then dried and cured for a period of time, preferably at a temperature sufficient to effectuate a complete covering of the metal particles previously adhered to the target fabric surface. For example only, a temperature between about 300xc2x0 and 450xc2x0 F.; preferably between 310xc2x0 and 400xc2x0 F.; more preferably from 325xc2x0 and 385xc2x0 F.; and most preferably between 350xc2x0 and 370xc2x0 F. are workable. Times of from 2 to 30 minutes are preferred for this drying and curing step with a time between about 2 and 10 minutes most preferred.
Any other standard textile additives, such as dyes, sizing compounds, and softening agents may also be incorporated within or introduced onto the surface of the apparel fabric substrate. Particularly desired as optional finishes to the inventive fabrics are soil release agents which improve the wettability and washability of the fabric. Preferred soil release agents include those which provide hydrophilicity to the surface of polyester. With such a modified surface, again, the fabric imparts improved comfort to a wearer by wicking moisture.
The preferred soil release agents contemplated within this invention may be found in U.S. Pat. Nos. 3,377,249; 3,540,835; 3,563,795; 3,574,620; 3,598,641; 3,620,826; 3,632,420; 3,649,165; 3,650,801; 3,652,212; 3,660,010; 3,676,052; 3,690,942; 3,897,206; 3,981,807; 3,625,754; 4,014,857; 4,073,993; 4,090,844; 4,131,550; 4,164,392; 4,168,954; 4,207,071; 4,290,765; 4,068,035; 4,427,557; and 4,937,277. These patents are accordingly incorporated herein by reference.
Another significant characteristic of this fabric is its ability to prevent migration of insulating materials, feathers, down, and synthetic fibers, through the fabric""s thickness. The ability of the fabric to prevent the migration of insulating materials is maximized when the voids at the interstices between overlapping yarns in the fabric are minimized and is achieved in this fabric through a combination of high yarn count construction, polyurethane coating, and calendering. Evaluating the ability of the fabric to prevent insulation migration was achieved using Federal Standard 191, Test Method 5450 (ASTM standard D737). A reduction in air permeability directly relates to a reduction in insulation migration through the fabric. To further reduce air permeability, a number of approaches have been taken. U.S. Pat. Nos. 5,073,418 to Thornton et al.; 5,011,183 to Thornton et al.; 4,977,016 to Thornton et al.; and U.S. Pat. No. 4,921,735 to Bloch, all of which are incorporated herein by reference, disclose providing low permeability characteristics through the use of mechanical deformation processes, e.g., calendering, to close the voids at the interstices between overlapping yarns in the fabric. Calendering of the present fabric may be carried out at any suitable point in its manufacture, e.g., prior to coating with metal particles, after metallizing but before treatment with polyurethane latex, or after such treatment.
Preferably, the metallized fabric of the present invention has an air permeability of not greater than 5 and not less than 1 cubic feet per minute (cfm) per square foot of fabric at a differential pressure of water at 125 Pascals of differential pressure, when measured in accordance with Federal Test Method 5450. Most preferably, the air permeability is equal to about 3 cfm, to allow some air flow through the fabric so that the insulating materials can dry after exposure to moisture, yet prohibit the migration of insulation, e.g., down, through the fabric.
The fabrics of the present invention are particularly well suited as inner-layer barrier fabrics such as liners for cold weather garments, pillows, sleeping bags, comforters and disposable industrial garments (e.g., protective and medical barrier apparel), due to their ability to 1) retain a substantial amount of metal particles within and on the target fabric after a long duration of wear and repeated standard launderings; 2) retain a substantial amount of heat due to the presence of a large amount of heat-reflecting metal particles within and on the target fabric; and 3) prohibit the migration of insulating materials, e.g., feathers, down and synthetic materials such as hollow fibers, through the fabric.
The following examples are indicative of the preferred embodiment of this invention: